Unlock Raiden Player Skin

Unlockables through Uplay

Sign in to Uplay from the Man Menu and select "Rewards". You can purchase goodies here using the points you earn for getting 4 different trophies in the Single Player game. They are:
Technical Difficulties
Perfectionist
Deja Vu
A knife to the heart

Unlockable

Purchase it for 20 points from Uplay

Altair's Armor

Purchase it for 20 points from Uplay

Altair's Costume

Purchase it for 10 points from Uplay

Assassin's Creed: Brotherhood Theme (for XMB)

Purchase it for 20 points from Uplay

Florentine Noble Attire

Purchase her for 40 points from Uplay

Hellequin (for Multiplayer)

Contributed by:
Farhan_Malik

Rewards

Different rewards can be unlocked for completing various in-game tasks.

Unlockable

Complete all 6 Romulus Lairs and unlock the Romulus treasure room

Armor/Dagger of Brutus

Attain rank 1 in the Mercenaries Guild challenges

Bartolomeo's Axe

Attain rank 5 in Courtesans guild challenges

Courtesans poison guards

Attain rank 5 in the corresponding guild challenges

Faction crest

Attain rank 10 in the corresponding guild challenges

Faction discount

Attain rank 1 in the Thieves Guild challenges

La Volpe's Bite

Attain rank 1 in the Courtesan Guild challenges

Maria's Dagger

Destroy all of Leonardo Da Vinci's War Machines

Parachute

Complete all assassins guild challenges

Sword of Altair and assassins crest

Attain rank 5 in Thieves guild challenges

Thieves pickpocket guards

Renovate all stables in Rome

War horse spawned at stables

Contributed by:
Jagglenuttz

Capes

Perform the following actions to unlock additional capes for Ezio. You can wear capes by equipping them in the Inventory menu.

Take the lead 10 seconds before the end of the session and go on to win (Multiplayer Only).

Strong Closer

Complete an entire Session with at least one kill (Multiplayer Only).

Synchronization Established

Attempt to access DNA Sequence 9 for the first time.

Technical Difficulties

Win the highest bet at the Fights.

The Gloves Come Off

Burn All Borgia Towers.

Tower Offense

Discover the Shrine in the Catacombe di Roma.

Undertaker 2.0

Complete DNA Sequence 8.

Vittoria Agli Assassini

Train a recruit up to the Rank of Assassin.

Welcome to the Brotherhood

Throw money in a well

Your Wish is Granted

Contributed by:
R351D3NT3V1L4

Guild Rewards

By leveling up the guilds you can obtain certain items for ezio to use.
You will unlock these at ezio's hidout.

Unlockable

Get Courtesans Guild to Level 3

Get Thieves Guild to Level 3

Get Mercenaries Guild to Level 3

Complete all Assassins Guild Challenges.

Get Courtesans Guild to Level 2

Courtesans Guild Crest

Get Mercenaries Guild to Level 2

Mercenaries Guild Crest

Complete all Assassins Guild Challenges.

Sword of Altair

Get Thieves Guild to Level 2

Thieves Guild Crest

Contributed by:
partydevil

How To Get The Scimitar & Other Non-purchasable Weapons

The heavy sheath is needed for this glitch to work. Equip a heavy weapon and throw it, then take the wanted weapon and sheath it. Now, replay the sequence 2 memory wherein Niccolo has you buy equipment. You will now find the weapon in the cupboard of the hideout's weapon room.

Ezio returns in Assassin's Creed: Brotherhood as he struggles against the powerful Templar Order . Defeating the corrupt tyrants entrenched there will require not only strength, but leadership, as Ezio commands an entire Brotherhood that will rally to his side.